Adds _postgis_scripts_pgsql_version() and _postgis_pgsql_version()
internal functions, each returning an encoded version number,
and has postgis_full_version() compare running vs. build-time used
Always show PGSQL version scripts were built against
References #3822 for 2.3 branch
git-svn-id: http://svn.osgeo.org/postgis/branches/2.3@16267 b70326c6-7e19-0410-871a-916f4a2858ee

Explicitly specify $(PERL) to call create_unpackaged.pl otherwise at least on freebsd it fails (and backport other minor changes like remove of 9.1 which support was dropped in 2.2)
Closes #3938 for PostGIS 2.3.6
Also add the Bessie sisters to battery testing
git-svn-id: http://svn.osgeo.org/postgis/branches/2.3@16124 b70326c6-7e19-0410-871a-916f4a2858ee